An azimuth sensor (geomagnetism sensor) detects the direction of geomagnetism and thereby measures an azimuth. Here, the geomagnetism as the target of measurement is extremely feeble. Accordingly, for accurate detection of the azimuth, it is necessary to detect the true geomagnetism by canceling offsets ascribable to magnetic fields present in the environment (one produced inside the set that incorporates the azimuth sensor, one produced by a strong magnet or the like placed near the azimuth sensor, and the like) and offsets ascribable to the performance of the azimuth sensor itself.
Offsets for an azimuth sensor constantly vary both temporally and spatially. Accordingly, for accurate detection of an azimuth, it is necessary to keep canceling the offsets for the azimuth sensor continuously and at high speed.
Offsets can be corrected either manually by the user doing it consciously or automatically without the user being conscious of it. For better user-friendliness and enhanced detection accuracy of the azimuth sensor, automatic correction is preferred.
One example of conventional technology related to what is discussed above is seen in Patent Document 1 identified below.